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Karlsruhe, Germany

Winterwerp J.C.,Deltares | Winterwerp J.C.,Technical University of Delft | Wang Z.B.,Deltares | Wang Z.B.,Technical University of Delft | And 3 more authors.
Ocean Dynamics | Year: 2013

This is Part II of two papers on man-induced regime shifts in small, narrow, and converging estuaries, with focus on the interaction between effective hydraulic drag, fine sediment import, and tidal amplification, induced by river engineering works, e.g., narrowing and deepening. Paper I describes a simple linear analytical model for the tidal movement in narrow, converging estuaries and a conceptual model on the response of tidal rivers to river engineering works. It is argued that such engineering works may set in motion a snowball effect bringing the river into an alternative steady state. Part II analyses the historic development in tidal range in four rivers, e.g., the Elbe, Ems, Loire, and Scheldt, all in northwest Europe; data are available for many decades, up to a century. We use the analytical model derived in Part I, showing that the effective hydraulic drag in the Ems and Loire has decreased considerably over time, as anticipated in Part I. We did not find evidence that the Upper Sea Scheldt is close to its tipping point towards hyperturbid conditions, but risks have been identified. In the Elbe, tidal reflections against the profound step in bed level around Hamburg seem to have affected the tidal evolution in the last decades. It is emphasized that the conceptual picture sketched in these papers is still hypothetical and needs to be validated, for instance through hind-cast modeling of the evolution of these rivers. This will not be an easy task, as historical data for a proper calibration of the models required are scarce. © 2013 Springer-Verlag Berlin Heidelberg. Source

The first aim of the physical model investigation for the 5th unit in the Iffezheim: Rhine hydropower plant was to safeguard the design of the power plant's intake - as had been planned on the basis of the results of a numerical 3-D model.The subsequent sensitivity investigations at the entry to the intake of the hydropower plant which were carried out at roughly the same time as the construction work,; made it possible to fully realize the savings potential in construction. The concluding investigations in the downstream area of the power plant were driven mainly by the optimization of the flow through the entries into the fish ladder in order to recognize them more easily. The report closes with a comparison between the results of the model trials and the flow conditions that became established on the spot after the commissioning of the 5th unit. Source

The additional technical contract conditions for hydraulic (reinforced) concrete structures, ZTV-W LB 215, have been revised in 2012 due to recent experiences and knowledge, but also because of changing standards to the new Eurocodes. The ZTV-W LB 215 is based on the basis of structural engineering standards for design, manufacturing of concrete and execution of concrete structures as well as on the specific standard for concrete hydraulic structures. The article clarifies the main changes from the previous version of ZTV-W LB 215 which dates from 2004. Relevant changes are the hydraulic specific examples of exposure classes, the demands on the concrete concerning hydration, design and aftertreatment of construction and movement joints and regulations for surface concrete. The associated catalogue for the concrete construction works, StLk LB 215, has also been revised. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

After 30 years of use the reinforced steel of the superstructures of the sluice bridge Iffezheim showed remarkable reinforcement corrosion caused by the ingress of chlorides inside the hollow girders of the bridge. Static investigations have shown, that the damages due to corrosion could be compensated by relatively simple measures of mechanical strengthening if the corrosion process could be stopped. Due to the small measurements of the hollow girders, conventional repair, which means removal and replacement of the chloride contaminated concrete, was impossible. In case of the two hollow girders at the upstream side, in which large areas were affected by reinforcement corrosion, the only applicable rehabilitation method was the use of cathodic protection (CP) to avoid further corrosion. After carrying out a test installation in a small area of one hollow girder (described in detail in [1]), the CP method became part of a general rehabilitation of the bridge in the years 2010 and 2011. After planning of the CP-System, which was done by Ingenieurbüro Raupach Bruns Wolff (RBW), the installation works were supervised by RBW and the Federal Waterways Engineering and Research Institute (BAW). In this article, that has to be seen as a continuation of [1], details of planning and realization of the CP-installation as well as monitoring results after one and a half year of operation are given. Copyright © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Existing bridges have sometimes to be evaluated considering ship impact. Using present codes for accidental actions would often lead to rehabilitation measures or to new structures which might not be efficient regarding the rareness of serious ship collision events to bridges. Therefore a method has been developed to determine ship collision forces as time-dependent action for the remaining lifetime of an existing bridge. This method, called remaining life expectancy concept, is based on the design concept of DIN EN 1990 which is a reliability-based design procedure. It considers the principles of the common maintenance strategies and allows the safe and economic verification of existing bridges considering their experienced lifetime. The contribution explains the probabilistic methodology of modern ship impact determination by combining a load model with a collision model as it is used for the design of new bridges. The adaption to remaining lifetime adapted dynamic impact forces is shown. The method has been published in 2010 as a guideline by Bundesanstalt für Wasserbau. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

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